Method and device for condensed image recording and reproduction

ABSTRACT

According to an embodiment, the invention discusses techniques of encoding image data and decoding the encoded image data in an effective manner. As a result, recording and reproduction of data is optimized by compressing an image signal based on whether or not there exists a significant difference between two adjacent frames or units of image data.

This application is a Continuation of application Ser. No. 11/017,741,filed on Dec. 22, 2004, now U.S. Pat. No. 7,433,525, which is acontinuation of application Ser. No. 09/174,542, filed on Oct. 19, 1998,now U.S. Pat. No. 6,912,351, and for which priority is claimed under 35U.S.C. §120; and this application claims priority of Application No.98-20293 filed in Korea on Jun. 1, 1998 under 35 U.S.C. §119; the entirecontents of all are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Time Lapse recording and reproducingmethod for optical disks, and more particularly, to a device and methodfor recording and reproducing video data on and from an optical diskusing a Time Lapse recording/reproduction process.

2. Description of Related Art

Time Lapse recording devices and methods according to the related artare generally used in security systems for monitoring and recordingactivities in security sensitive areas, such as banks or museums. Arelated art Time Lapse Video Cassette Recorder (Time Lapse VCR) recordsand reproduces video signals on and from magnetic tapes.

FIG. 1 shows a block diagram of a general Time Lapse VCR. As showntherein, the Time Lapse VCR includes an A/D (analog-to-digital)converter 10 for converting an analog image signal input from a cameradevice, such as a CCD camera, into digital image data; a buffer memory21 for temporally storing the digital image data therein; a field memory22 for outputting the digital image data of the buffer memory 21 whenthe field memory 22 is full; a D/A (digital-to-analog) converter 30 forconverting the digital image data output from the field memory 22 intoan analog image signal; a recording/reproducing unit 40 for recordingthe analog image signal on a magnetic tape; an input unit 60 forreceiving a user's option or user's selection; and a controller 50 forcontrolling the read and write operation of the memories 21 and 22 andcontrolling to store the image data intermittently with a predeterminedtime interval according to the user input received from the input unit60.

The controller 50 selects each frame of the image data of the buffermemory 21 with a predetermined time interval which is based on therecording time set by the user's input, and stores each of the frames inthe field memory 22. In other words, the controller 50 transfers imagedata stored in the buffer memory 21 in frame units to the field memory22. As a result, time-sensitive image data are compressed and stored inthe field memory 22 in frame units.

When the field memory 22 is completely full, the controller 50 controlsthe recording/reproducing unit 40 to begin recording of an analog imagesignal output from the D/A converter 30. At the same time, thecontroller 50 continues to store the converted image data in the buffermemory 21. Upon completion of the recording operation, a frame of theimage data corresponding to a predetermined time interval is transferredfrom the buffer memory 21 to the field memory 22 and stored therein.This process is repeated to store an image signal in a Time Lapsemanner.

The Time Lapse VCR as described above must forwardly move and stop thetape repeatedly to continuously Time Lapse record the image signal basedon the size of the field memory 22. This results in considerable use andwear of the deck and drum of the conventional Time Lapse VCR, so thatthe drum and deck must be replaced frequently. Furthermore, the magnetictape on which the image signals are recorded and reproduced deterioratesquickly due to the friction against the heads 2 of the VCR. This affectsthe quality of image being displayed by the related art Time Lapse VCRand the life span of the VCR.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide arecording method for compressing and intermittently recording image dataon a recording medium with a maximum recording capacity.

Another object of the present invention is to provide a reproductionmethod for reproducing compressed intermittent data from a recordingmedium.

Another object of the present invention is to provide a method anddevice for decoding predictive coded image data, and a method and devicefor encoding image data.

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given here-in-below and the accompanying drawingswhich are given by way of illustration only, wherein like referencenumerals designate corresponding parts in the various drawings, andwherein:

FIG. 1 illustrates a block diagram of a Time Lapse VCR using memoryunits according to a related art;

FIG. 2 illustrates a block diagram of a Time Lapse recording apparatusaccording to an embodiment of the present invention;

FIG. 3 illustrates a flow chart depicting a recording method forintermittent data according to an embodiment of the present invention;

FIG. 4 illustrates a flow chart depicting a reproduction method forreproducing compressed intermittent data recorded on an optical diskaccording to an embodiment of the present invention;

FIGS. 5A and 5B illustrate examples of a logical data structure of adigital data stream compressed and recorded on the optical diskaccording to an embodiment of the present invention; and

FIG. 6 illustrates an example of a structure of a bit stream recorded onan optical disk according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A Time Lapse recording/reproduction device according to the preferredembodiments of the present invention intermittently records compressedimage data on an optical disc and reproduces the recorded image datawith a high operation speed.

FIG. 2 shows a block diagram of a Time Lapse recording/reproductiondevice according to an embodiment of the present invention. As shown intherein, the Time Lapse recording/reproduction device includes a switch80 for selecting one of analog image signals inputted in frame unitsfrom a plurality of cameras; an A/D converter 90 for converting theselected image signal into digital data by sampling the image signal ata predetermined rate; a plurality of frame memories 100 and 101 forstoring therein image data in frame units; an encoder 110 for generatingI-picture data or P-picture data in frame units by using transformationand quantization of image data output from the frame memory 100; arecording-digital signal processor (DSP) 120 for extracting movingvectors from the image data output from the frame memory 100 and forgenerating P-picture data of the compressed image data; a multiplexer130 (MUX) for multiplexing additional data into the compressed imagedata of the encoder 110; a record/reproduction unit 140 for recordingthe multiplexed data onto a recording medium, such as an optical disk 1,and for reproducing the recorded data from the optical disk 1; ademultiplexer (de-MUX) 131 for demultiplexing the reproduced data fromthe recording/reproducing unit 140 to generate moving vectors andcompressed image data; a decoder 111 for performing areverse-quantization and reverse-transformation of the demultiplexedimage data output from the de-MUX 131; a reproducing-DSP 121 forgenerating original image frames based on the P-picture data output fromthe decoder 111 and the moving vector output from the de-MUX 131; a D/Aconverter 91 for converting the reproduced image data into an analogimage signal; and a controller 150 for controlling the above-describedcomponents based on the commands from the user. Therecording/reproduction unit 140 includes video heads for reading and/orwriting information on the recording medium. Each of the frame memories100 and 101 can include a plurality of frame memory units. In addition,other types of memories may be used, instead of the optical disc 1.

FIG. 3 illustrates a flow chart depicting a recording method accordingto an embodiment of the present invention.

As shown therein, in Step S01, the controller 150 receives a channel(camera) selection signal input from the user and switches theconnection of the switch 80 to receive an image signal from the selectedchannel. A plurality of channels (camera) may be selected so that theswitch 80 selects the channels sequentially and repeatedly during apredetermined time period. The image signals, which are input from thecurrently selected camera, are sampled according to the sampling time ofthe A/D converter 90 for conversion into digital data, and are stored inthe frame memory 100 in frame units, in Step S02. That is, image dataare intermittently obtained and stored in the frame memory 100 accordingto the present invention.

In Step S03, the intermittent image data stored in the frame memory 100are read in frame units and transmitted to the encoder 110. The encoder110 relocates pixels forming the image data based on each frequencyvalue, and performs a transformation and quantization operation bydividing the pixels by each quantization value variably set according tothe frequency features of the relocated pixel areas.

According to the transformation and quantization operation, image data(first image data) is compressed and generated in the form of I-pictureframe data (first encoded data) by the encoder 110. The I-picture frame(intra-frame) data carries the entire image information of a frame. Thegenerated I-picture frame data is transmitted to the MUX 130, and alsostored in the frame memory 100 until it is updated by another image dataaccording to the process described below.

In Step S04, image data (second image data) subsequently following theimage data (first image data) just processed by the encoder 110 istransmitted from the memory 100 and converted into compressed image data(second encoded data) by the encoder 110. This encoded data is input tothe recording DSP 120.

In Step S05, the recording DSP 120 receives the encoded data (secondencoded data) and generates the image data (second image data) as itexisted before the data compression. Then the recording DSP compares therestored image data (second image data) with the prior I-picture orP-picture image data (first encoded data) stored in the buffer memory100 to generate a moving vector corresponding to changes between thesedata. In the recording DSP 120, the value of the detected moving vectorvalue is compared with a preset reference value in Step S06.

In Step S10, if the value of the moving vector is less than thereference value (i.e., little change between two frames), the restoredframe data (second image data) is output to the encoder 110 as a framethat has much less data than the I-picture frame, e.g., as a P-pictureframe in MPEG. This P-picture frame is compressed by the encoder 110,which is then transmitted to the MUX 130.

On the other hand, in Step S15, if the value of the generated movingvector is greater than the reference value, the restored image framedata is not generated as P-picture frame data, but is sent to the MUX130 as encoded I-picture frame data from the encoder 110.

In Step S11, if the restored image data is output as a P-frame (StepS10), the recording DSP 120 transmits to the MUX 130 the moving vectorand the position value of the corresponding (or previous) I-frame, sothat the above information is added to the corresponding compressedP-frame output from the encoder 110.

In Step S12, the controller 120 sends to the MUX 130 a camera (channel)identification code signal corresponding to the channel selection by theswitch 80, so that the camera ID code is added to a data packetincluding the corresponding image frame. In Step S13, the MUX 130selectively outputs the I-picture data (or P-picture data), the cameraID code, and the address of the I-picture data received from the encoder110, the recording DSP 120 and the controller 150, and generates a bitstream of certain bytes for each frame. These bit streams aretransmitted to the recording/reproducing unit 140 which records them onthe optical disk 1.

The bit stream generated and transmitted to the recording/reproducingunit 140 as described above has a logical structure as shown in, e.g.,FIG. 5A. As shown therein, each P-picture frame P1, P2, PS has a currentaddress CAD indicating the current address of the P-picture, and anI-picture reference address IAD indicating the address of thecorresponding (or previous) I-frame. If image signals are obtained frommore than one camera, the bit streams generated and transmitted to therecording/reproduction unit 140 can have a logical structure as shownin, e.g., FIG. 5B. In addition to the shown in FIG. 5A, the data streamof FIG. 5B includes a camera (channel) ID code CHID indicating theidentification code of each camera or a signal source.

FIG. 6 shows an example of a data structure of the bit stream shown inFIGS. 5A and 5B to be recorded and reproduced on and from the opticaldisk medium. As shown therein, the data structure is divided to carrythe physical address of the bit stream (1), the camera ID code (2), theaddress of the corresponding I-picture frame (3), and picture datastored in the picture data area (4). In the first bit stream B1, theI-picture data are stored in the picture data area (4) so that theaddress of the corresponding I-picture frame (3) is zero or absent. Inthe second bit stream B2, the P-picture data are stored in the picturedata area (4) so that the address of the corresponding I-picture frame(3) is included in the bit stream. During reproduction, the address ofthe corresponding I-picture frame (3) is detected to retrieve from thataddress the corresponding I-picture frame data for the P-picture framedata.

FIG. 4 illustrates a flow chart depicting a reproducing method forreproducing compressed intermittent data (e.g., as shown in FIG. 6)recorded on a recording medium, such as an optical disk, according to anembodiment of the present invention.

As shown in Steps S21 and S22 of FIG. 4, if the user requestsreproduction of an image data from a particular camera or channel amongthe intermittent image data recorded on the optical disc 1, thecontroller 150 controls the recording/reproducing unit 140 to reproducethe corresponding image data from the optical disc 1. The image datareproduced from the optical disc 1 is multiplexed data, which isdemultiplexed by the de-MUX 131. By demultiplexing, the camera (channel)ID code CHID is separated from the reproduced image data and output tothe controller 150. Based on the camera ID code CHID, the controller 150determines whether or not the reproduced image data corresponds to theselected camera or channel, in Step S23. This ensures that the correctimage data is processed to comply with the user's request. If incorrectimage data has been reproduced, the controller 150 controls therecording/reproduction unit 140 to reproduce the correct image data fromthe optical disc 1.

In Step S30, the image data corresponding to the user's request istransmitted and decoded in the decoder 111. The decoding process of thedecoder 111 involves reverse-quantization and reverse-transformation torestore the original image data prior to data compression carried outduring recording. Then the property (type) of the currently restoredimage data is determined in Step S31 by the reproducing DSP 121, and thedetermination result is transmitted to the controller 150. Morespecifically, if the currently restored image data is detected to beP-picture frame data in Step S32, the controller 150 stores the currentreproduction position in Step S33. Then in Step S34, the controller 150detects the address of the corresponding I-picture frame (e.g., datastored in the area (3) of the bit stream B2 shown in FIG. 6) from thereproduced image data output from the de-MUX 131, and reproduces basedon the detected address the corresponding (or previous) I-picture framedata recorded on the optical disc 1 by controlling therecording/reproduction unit 140.

In Step S36, the reproduced corresponding I-picture frame data isprocessed by the reproducing DSP 121, and decoded by the decoder 111 tobe stored in the frame memory 101. The controller 150, after Step S36,controls the recording/reproducing unit 140 to move the video heads tothe original recording position stored in Step S33.

In Step S38, in the reproducing DSP 121, the P-frame corresponding tothe user's request signal is restored as a full screen image(background) using the corresponding I-picture frame data stored in theframe memory 101 and using the moving vectors obtained from the de-MUX131. Then the full screen image data is reverse-transformed andreverse-quantized by the decoder 111, and stored in the memory 101 asthe original image data corresponding to the user's request signal. Thefull screen image data is converted into an analog image signal by theD/A converter 91 and output as a reproduction signal in Step S39.

On the other hand, in Step S32, if the detected image data is not aP-picture frame, then the detected image data is decoded by the decoder111 as described above, and output as an analog image signal from theD/A converter 91 in Step S39.

When the image data corresponding to the user's request signal isP-picture frame data, full screen image data can be obtained byretrieving corresponding or prior I-picture frame data based on theI-picture frame address recorded with the P-picture frame data.

According to the present invention, recording and reproduction of datais optimized by compressing an image signal based on whether or notthere exists a significant difference between two adjacent frames. As aresult, the recording medium can record thereon and reproduce therefroma significantly greater amount of image data compared to conventionalrecording and reproduction devices and methods. When the recording andreproduction of a moving picture is carried out by a camera, such as aCCD, a CCTV, etc., only the desired images can be selectively reproducedwith high display quality. Further, use of an optical disc permits afaster and more selective access of all image data stored thereon.Moreover, digital recording and reproduction of signals results in animproved picture quality.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodification as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A method for decoding coded image data, the method comprising:receiving the coded image data, wherein some of the coded image data hasan ID indicator that is based on a reference image to detect thereference image based on the ID indicator, and other coded image datadoes not include the ID indicator that is based on the reference image;detecting the reference image based on the ID indicator when the codedimage data has the ID indicator that is based on the reference image;obtaining moving vector information related to the reference image; anddecoding the coded image data based on the detected reference image andthe obtained moving vector information when the coded image dataincludes the ID indicator, and decoding the coded image data based onitself when the coded image data does not include the ID indicator. 2.The method of claim 1, wherein the ID indicator indicates addressinformation of the reference image.
 3. The method of claim 2, furthercomprising: storing the reference image, address information of thereference image, and camera code information for the reference image inone location.
 4. The method of claim 1, further comprising: storing thecoded image data and the corresponding ID indicator together in onelocation.
 5. An apparatus for decoding coded image data, the apparatuscomprising: a receiving unit configured to receive the coded image data,wherein some of the image data has an ID indicator that is based on areference image to detect the reference image based on the ID indicator,and other coded image data does not include the ID indicator that isbased on the reference image; a detecting unit configured to detect thereference image based on the ID indicator; an obtaining unit configuredto obtain moving vector information related to the reference image; anda decoding unit configured to decode the image data based on thedetected reference image and the obtained moving vector information whenthe coded image data includes the ID indicator, and to decode the codedimage data based on itself when the coded image data does not includethe ID indicator.
 6. The apparatus of claim 5, wherein the ID indicatorindicates address information of the reference image.
 7. The apparatusof claim 6 further comprising: a storage unit configured to store thereference image, address information of the reference image, and cameracode information for the reference image in one location of the storageunit.
 8. The apparatus of claim 5, further comprising: a storage unitconfigured to store the said some of the coded image data and thecorresponding ID indicator together in one location of the storage unit.